Heat insulating covers for heat-insulating an engine disposed in an engine compartment provided in the front side of a vehicle are known in the art. Patent Document 1 discloses a heat insulating cover including an engine compartment encapsulation member surrounding the upper portion of a power train configured as an assembly of an engine and a transmission in an engine compartment. The engine compartment encapsulation member includes a top cover for covering the upper portion of the engine compartment, and right and left side covers for covering side surfaces of the engine compartment, the top cover and the left and right side covers being integrally formed with one another. A rear cover is integrally formed with the top cover and the left and right side covers at rear edges of these covers closer to the rear of the vehicle, and covers a rear surface of the engine compartment. The engine compartment encapsulation member has an open surface closer to the front of the vehicle to introduce and discharge air.